I need help making my html document detect machine browsers

hey I’m creating a flash site-which is now complete-that is going to run through dreamweaver, which has both flash and hml versions of the site, I am using dreamweaver mx 2004 and I need to figure out the onLoad()…if, then statements nessesary to test for a specific browser-either mac safari or win netscape 5.5+ so I can utilize the onLoad(), resizeTo, moveTo, functions of the javascript to open my cromless windows centered in the middle of the page. I have the scripts completed for the cromless windows that open perfectly when assigned to a specific engine, either safari or netscape, but one script will default and fail if it is opened in the other browser, I know that netscape doesn’t use the a> coding of html as well as safari so I need to have seperate codes employed when the onLoad() detects for which browser is currently being used on the machine. so a basic on run array would follow like this:
user accesses main page
HTML and Flash option buttons
//well forget about the HTML since everyone can read it
Flash Button is Pressed
onLoad(), local machine detects browser
if Safari-then load mac safe script
//this pops a centered-chromless window
runs flash document
else if Netscape, then load win/netscape friendly script
//this pops the netscape chromless centered window
runs flash document
any ideas or scripts would be a lifesaver,
also if anyone can do this with less coding…i.e, the javascript that runs seamlesly between platforms for the chromeless popup, that would be more than appriciated, thanks